EP0229645B1 - Process for producing an antifalsification paper with an incorporated security element - Google Patents

Abstract

To produce a security paper with an embedded security feature (7) therein in the form of a thread, band or the like, a first layer of paper (3) and a second layer of paper (5) in a second papermaking machine are produced and the security feature (7) is inserted in a defined position between these layers (3, 5). After this, these are pressed together and dried. The individual paper layers (3, 5) can be provided with watermarks (9) or apertures (10, 11) at specific locations with respect to the thread (7), whereby the thread can be specifically exposed at pre-determined positions. <IMAGE>

Description

The invention relates to a method for producing a security paper with a security element embedded in the paper in the form of a thread or tape, the security element being present at least locally in areas of reduced paper thickness or on the surface of the paper.

Security papers, such as those used for banknotes, securities, documents, ID cards, etc., usually have watermarks that prove the authenticity of the paper. These papers are produced on circular screen paper machines, it being known that elevations and / or water-impermeable areas on the screen surface bring about the reduction in fiber deposition necessary for the formation of the watermarks. The finished paper sheet then has locally different paper thicknesses and in this way images or patterns can be introduced which show the effect of the contrast reversal typical of the watermark when viewed in reflected and transmitted light.

Furthermore, it is known to incorporate a security element in the form of a thread or tape etc. into the paper layer. For this purpose, the thread is introduced into the paper pulp and brought up to the sieve in such a way that it lies there after the fiber deposition has started, that is to say a fiber layer has already formed but has not yet been completed, so that the thread is then complete in the finished sheet is included. This storage process is well known and e.g. described in DE-OS-24 08 304 (Jung).

It is sometimes unavoidable, for example if the design of the banknote requires that the thread also be stored in the area of a watermark. Since the fiber layer is relatively thin in the clear areas of the watermark, the incorporation of the thread in these areas can considerably interfere with the fiber layer formation in accordance with the known method. The thread can deposit, for example prevent the fibers, so that the paper fiber layer is interrupted at these points and the thread is then exposed there. The introduction of the thread in the watermark area is therefore very problematic, since a large number of framework conditions such as the thread insertion point, height of the watermark relief, sieving speed, etc. must always be optimally met in order to achieve correct storage of the thread. Since all conditions cannot always be met at the same time and to the same extent, this results in high rejection rates under unfavorable conditions.

With certain threads, it is sometimes desirable for the thread to be partially exposed. Threads that e.g. a print sample or other visually verifiable features such as Diffraction structures, dichroic materials, etc., can namely be easily checked in this way. It is known from GB-PS-1 552 853 to store such visually inspectable security threads in such a way that they lie locally freely on the paper surface. This can e.g. can be achieved by subsequently removing the paper layer in certain areas of the security thread or by storing the security thread in the watermark area as described above, so that the thread is only covered by a thin and thus almost transparent paper layer.

In particular due to the above-mentioned problems with the insertion of a thread in the watermark area known to the person skilled in the art, the person skilled in the art can also take advantage of the critical parameters and the process parameters mentioned above for inserting a security thread such as the time of insertion of the thread, embossing structure on the sieve, etc. choose that the thread in the finished paper web is not only covered by a thin paper structure, but is completely exposed. This process is described, for example, in EP-A-59 056 (Portals) also described in more detail. The thread is then, of course, introduced according to this request so that it comes to rest on the raised and / or water-impermeable areas of the sieve before a separation of fibers has taken place here.

The problem with this process, however, is that a large number of parameters must be constantly observed in this process in order to obtain the desired product in sufficiently good quality. Furthermore, the thread must be inserted under such a tension that it bridges the areas between the relief elevations of the sieve freely and it does not come to rest on the sieve. In addition, the fiber deposition around the thread, in particular in the bridging area, must not be impeded, although only one-sided “windows” can be produced with this method, even if all parameters are observed.

GB-PS-1 486 079 finally discloses a method for completely embedding relatively wide security threads in paper, the security tape being embedded between two separately produced paper webs and the overall arrangement then being pressed and dried.

The object of the invention is now to provide a method for producing security papers, the thread being able to be embedded without problems both in almost any layer depth in the paper and in the watermark area, and furthermore there being the possibility of also placing the thread at any point on the Expose the front and back of the paper so that it is accessible for visual inspection in reflected light.

This problem is solved by the procedure specified in the characterizing part of the main claim.

The basic idea of the invention is that the thread insertion is decoupled from the fiber layer formation on the paper screen, so that the thread insertion cannot have a disruptive effect on the actual fiber layer formation (sheet formation).

One or both paper layers can now be produced very thin locally without any problems, with at least one of the paper layers in the thread area being locally reduced to a thickness of 30-0% with respect to the overall total thickness of both layers for good visual visibility of the thread.

Despite the fact that the paper layers enclosing the thread are produced on separate paper sieves, due to the rapid merging of these layers and the joint gumming and drying, a non-separable paper sheet is produced which, with regard to its internal strength, does not produce from one on only one sieve Paper sheet differs.

By creating the individual components of the security paper on two separate sieves and inserting the security thread between the two layers, there are a number of options for storing the thread in a visually clearly visible form in the paper.

For example, fiber layers of different thicknesses can be produced on the first and second paper sieves, preferably in a thickness ratio of 1: 4. The thread comes to lie near the surface in the finished sheet, which improves its visual inspection over the entire length of the paper. A lettering, for example, on the thread is over the entire Thread length legible.

Furthermore, watermark patterns can be placed in one or both layers of paper e.g. in the form of several regularly repeating areas in e.g. rectangular, round or elliptical shape. The thread that is embedded in these areas is then only overlaid on these surface areas by a thin layer of paper and is therefore clearly visible there.

The measures required for forming the watermark pattern on the screen (elevations, water-impermeable areas) can also be designed in extreme cases so that there is no fiber deposition there and holes are thus created in the fiber composite. This makes it possible to expose the thread in a targeted manner.

If both layers of paper are provided with such a watermark or hole pattern, a security paper can be produced by coordinating the arrangement of the watermark patterns and synchronous running of the two paper screens, the thread e.g. alternately appears at regular intervals on the front or back of the finished sheet.

Further advantages and advantageous developments are the subject of the dependent claims and the content of the description of the invention with reference to the figures.

• Fig. 1 eine Vorrichtung zur erfindungsgemäßen Herstellung eines Sicherheitspapiers,
• Fig. 2 den Vorgang der Fadeneinführung zwischen die Papierschichten,
• Fig. 3-7 verschiedene nach dem erfindungsgemäßen Verfahren hergestellte Sicherheitspapiere im Querschnitt.

The figures show:

• 1 shows a device for producing security paper according to the invention,
• 2 shows the process of thread insertion between the paper layers,
• Fig. 3-7 different security papers produced by the method according to the invention in cross section.

1 shows an exemplary embodiment of a device for producing a security paper. The device corresponds essentially to the commercially available paper machines, which has at least two separate wet sections. The preferred embodiment shown here consists of a combination of two circular screen wet sections 1 and 2, a so-called double circular screen paper machine. In the wet section 1, a first paper web 3 is scooped, which is then suspended under the take-off felt 4 over a distance of approximately 2 m to the second wet section 2. In the second system 2, a second paper web 5 is scooped. Both paper webs are combined at the location of the roll 6 and then run together to the further processing stations, in which the paper is pressed and dried (not shown in the figures).

Before the unification of the paper webs, a security thread 7 is introduced between these webs, which is unrolled from a supply roll 8 and guided to the unification point via a guide roll 9. This process is shown in an enlarged detail in FIG. 2 (a true-to-scale representation has been dispensed with in order to better illustrate the facts). The security thread can be guided in such a way that, as shown in FIG. 2, it is detected simultaneously by both layers of paper. It can also be placed on the second paper layer 5 after it has left the pulp. When the layers of paper are combined, the thread is then enclosed between the layers of paper.

Preferably, two circular screening plants are used for the production of the two paper layers. However, it is also possible to embed the security thread between two layers of paper produced on four-wire systems or to use a combination of a four-wire and a rotary screen system for producing the two paper layers. The use of circular sieves is preferred because it can produce very high-contrast and good watermarks.

The separate production of the two layers of paper on two separate circular screen systems and the embedding of the thread between these paper webs result in a wide range of design options for the final product. The respective procedures for producing individual exemplary products are subsequently explained with reference to FIGS. 3-7.

To increase the security against counterfeiting, security threads are often used which, for example, have lettering or contain other visually verifiable optical features. Such features are, for example, diffraction gratings. In order to be able to test such threads in a simple manner, it is necessary that they be visually accessible. The method according to the invention now allows threads of this type to be embedded without problems near the surface of the security paper. For this purpose, different thicknesses are selected for the paper layers produced on both paper machines, preferably in a thickness ratio of 1: 4. A paper layer 3 is produced in the first paper machine, the thickness of which will be reduced to approx. 80 μm after Gautschen and drying. While the thinner paper layer 5 is produced in the second paper machine, which will reduce to 20 μm after the further processing operations. The security thread 7 embedded between these paper layers is thus only 20 µm from one side of the finished paper covered with a thick layer of paper, making it easy to check visually. In this way, the thread can be placed very close to the surface of the paper, which is always very difficult according to the conventional embedding method for security thread. According to the conventional methods, in order to achieve the same effect, the thread must be brought to the screen either very early or very late. However, there is the major problem that it is difficult to avoid the thread emerging at least in places from the fiber composite.

In Fig. 4 a product is shown, wherein one of the paper layers 5 is provided with a water oak 9, so that the thread is overlaid on one side of the paper at silted places only by a thin layer of paper and is therefore clearly visible at these points .

5 shows a further embodiment, both paper layers 3 and 5 being equipped with a water oak. The elevations on the sieve or impermeable points necessary for the formation of the water oak are designed so that the respective water oak patterns complement each other to form a positive / negative relief. If the two paper sieves run in a synchronous manner, the thread is then guided in places near one surface and then shifted onto the opposite surface. The finished sheet then has a uniform thickness, while the thread appears on both sides of the sheet at regular intervals.

The measures on the paper screen required for the production of water oak, for example the increase in relief, can also be designed to such an extent that fiber deposition is completely prevented there. According to the example shown in FIG. 6, one of the two paper layers is manufactured according to this concept. The paper layer 3 has holes 10 at regular intervals on and the thread 7 inserted in these areas is completely exposed through the holes in the paper layer. The perforated paper web can have the same thickness as the opposite paper web or a smaller one.

According to a further exemplary embodiment, both paper webs 3 and 5 can also be provided with such a hole pattern 10 or 11, which results in further design options. The circular sieves can be shaped and synchronized in their run in such a way that the hole patterns coincide when the two paper webs are joined. The thread 7 is thus exposed in the same place on both sides. Threads that e.g. show different appearance when viewed in reflected or transmitted light, can thus be easily checked. On the other hand, the holes can also be arranged so that they are offset from one another in both layers of paper. However, the alternating sequence of the holes is preferably chosen, since in this case the thread is always surrounded by a paper fiber layer on at least one side and thus adheres firmly to the fiber composite.

The holes or the thinned areas in the paper layer produced with the first system can also be produced shortly before or after removal of this web from the circular screen. If, for example, an air or water jet is directed onto a paper layer, this causes a local displacement of the fibers and craters or holes can be produced in the paper layer. The use of an air or liquid jet device also facilitates synchronization if the patterns in the two layers of paper are to be coordinated. The air or liquid jet device is then activated synchronously with the running of the second paper web or the second circular screen.

The examples shown here are based on the use of a twin-wire machine. However, the method according to the invention can easily be extended to larger systems with more than two wet sections, which makes it possible to embed several threads in different layers of the paper. These threads can then lie side by side or one above the other. Furthermore, there is also the possibility that the paths of the individual threads e.g. cross over. According to the method according to the invention, this is possible in a simple manner, since the threads are introduced into the paper independently of one another at different locations, whereas such a course of several threads cannot be achieved according to the conventional insertion methods.

For better clarity, the examples shown in FIGS. 3-6 are only basic representations. As is known, a displacement within the fiber structure is caused in the watermark area by the pressing action required when the paper layers are removed from the wire and in particular by the subsequent rubber and drying processes. In the thin areas the fiber layer is e.g. shifted to the center plane of the paper so that the relief height is approximately the same on both sides of the paper. This shift will also change the position of the thread in relation to the middle plane of the paper. The thread in the final product is therefore not always in one plane, as shown in the figures, but will be pressed out of this plane at the points of reduced paper thickness.

Claims (12)

1. Process for producing an anti-falsification paper with a security element embedded in the paper in the form of a thread or strip, the security element being present at least locally in regions of minimum paper thickness or at the surface of the paper, characterised in that

- a first layer of paper is formed in a first wet end of a paper machine, and is released from the cloth by means of a removal band,

- a second paper layer is formed on a second wet end of a paper machine,

- one or both paper layers have at least local regions of reduced thickness amounting to up to 30% of the total thickness of both layers,

- the first paper layer is transported by means of the removal belt on to the second paper layer and brought into intimate contact with it, the security element being introduced between the paper layers in such a way that it is arranged in the regions of low paper thickness or openings in one or both paper webs,

- the combined paper webs are together calendered and dried.

2. Process according to claim 1 characterised in that the regions of low thickness in the or each paper layer are produced by regions printed in relief on the cloth or regions on the cloth of deliberately reduced water permeability, the deposition of fibres in these regions being reduced or entirely suppressed.

3. Process according to claim 1 characterised in that at least one of the two paper layers is treated with a stream of air or water during the formation of the sheet or shortly afterwards in such a way that deliberate local compression of the fibres is achieved, to the point of forming holes.

4. Process according to claim 1 characterised in that the two paper layers are produced with different thicknesses, preferably in the ratio of 1: 4.

5. Process according to claim 1 characterised in that at least one of the two paper layers is produced on a cylinder screen machine.

6. Process according to claim 1 characterised in that periodically repeating watermark regions or holes are introduced into both paper layers.

7. Process according to claim 6 characterised in that the watermarks of the one layer of paper are formed with regard to the thick and thin regions of paper to be complementary to the watermarks of the other paper layer.

8. Process according to claim 6 characterised in that the watermarks or holes of both paper layers are arranged over one another when the layers are brought together so that the thick regions of the watermarks of the one paper layer lie over the corresponding thin regions or holes of the other paper layer.

9. Process according to claim 6 characterised in that the two paper layers are brought together so that the watermarks or holes of the one paper layer come to lie between the watermarks or holes of the other paper layer.

10. Process according to claim 1 characterised in that the regions of low thickness in the paper webs are formed as simple geometric patterns, in particular in the form of substantially rectangular, round or elliptical surface regions.

11. Process according to one or more of the foregoing claims characterised in that further paper machines are connected to the first and second paper machines and that further security elements are introduced between the individual machines into the paper web which is made up of several layers.

12. Process according to claim 11 characterised in that the security elements between the different paper layers are arranged alongside and/or over one another and/or that the security elements intersect.

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